Wikipedia defines Wafer level packaging (WLP) as the technology of packaging an integrated circuit while still part of the wafer, in contrast to the more conventional method of slicing the wafer into individual circuits (dice) and then packaging them. WLP is essentially a true chip-scale package (CSP) technology, since the resulting package is practically of the same size as the die. Wafer-level packaging allows packaging, test, and burn-in at wafer level at the fab in order to streamline the manufacturing process undergone by a device from silicon start to customer shipment of packaged system.
Wafer-level packaging includes extending the wafer fab processes to include device interconnection and device protection processes. Most other kinds of packaging do wafer dicing first, and then put the individual die in a plastic package and attach the solder bumps. Wafer-level packaging involves attaching the top and bottom outer layers of packaging, and the solder bumps, to integrated circuits while still in the wafer, and then wafer dicing.
It has been found that very low pressure levels should be maintained within a WLP wafer for a wide range of MEMS devices.
There is a growing need to provide a reliable manner of measuring the pressure level within the MEMS systems that are implemented on a WLP wafer. Especially for measuring the pressure levels at one or more points in time after the WLP package has been diced and elements of the WLP outgas thereby increase the pressure level within the MEMS systems.